1. Technical Field
The present invention relates to a vehicle seat belt retractor, and particularly to a retractor in which withdrawal of belt webbing is blocked in response to sudden vehicle deceleration such as occurs in a vehicle collision.
2. Description of the Prior Art
A typical seat belt system used to restrain a vehicle occupant includes a length of belt webbing wound on a spool of a seat belt retractor. The belt webbing is extensible about a vehicle occupant to restrain the occupant. In the event of sudden deceleration such as occurs in a vehicle collision, a vehicle deceleration sensing assembly in the retractor is actuated to block withdrawal of the belt webbing from the retractor.
A typical vehicle deceleration sensing assembly includes an inertia mass which, in the event of sudden vehicle deceleration, moves relative to other parts of the retractor. The movement of the inertia mass actuates a locking mechanism to block rotation of the spool on which the seat belt webbing is wound.
It is desirable that a vehicle deceleration sensing assembly be operable when the retractor is in a plurality of different inclined orientations. Thus, if the retractor is, for example, mounted in a reclinable vehicle seat back, the sensing assembly should preferably be operable when the seat back is reclined at different positions. U.S. Pat. No. 5,289,986 discloses one such type of vehicle deceleration sensing assembly.